drysdale



No. 622,738. Patented Apr. II,, 1899. T. B. VOCE' & B. DRYSDALE.

Y SPROCKET DRIVING WHEEL.

(Application filed Feb. 12, 1898.)

3 Sheets-Sheet I.

(No Model.)

No. 622,738. Patented Apr. ll, I899. T. R. VOCE & B. DBYSDALE.

SPBOCKET DRIVING WHEEL. (Application filed Feb. 12, 1898.) (No Model.)

FIG. 5

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No. 622,738. Patented Apr. ll, I899. T. R. VOCE & B. DRYSDALE.

SPBOCKET DRIVING WHEEL.

(Applicction filed Feb. 12, 189 6.)

NlTE STATES FFlCEt P TEN SPROCKET DRIVING-*WHEEL;

SPECIFICATION forming part of Letters Patent NO. 622,738, dated .April11, 1895.

Application filed February 12,1898. erial No. 670,050. (No model.)

'To (LZZ whom it may concern:

. Be it known that we, THOMAS REGINALD Voon and BRUCE Dnvsnn LE,manufacturers, subjects of the Queen of Great Britain, residing at 176Bolton road, Small Heath, Birmingham, in the county of WVarWicl England,have invented certain new and useful Improvements in SprocketDriving-Wheels for Cycles and other Purposes, (for which we have madeapplication for Letters Patent in England, No. 16,098, dated July 14L,1897;) and we do hereby declare the followingto be afull, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

Our invention has for its object improvements in sprocket driving-wheelsfor cycles and other purposes by which we are enabled to greatly reducethe friction which exists in sprocket-wheels as at present constructedand also to adjust the teeth to suit the pitch of the drivingchain.

lVe have termed' our invention the expanding chain-wheel.

In carrying our invention into practive we form our sprocket or chainwheels from two rings, between which the teeth are secured. These teethare pivoted to the rings and are free to move and adjust themselves tothe variations in the pitch of the chain, each tooth having a projectionat one side at its base at right angles to itself extending around aportion of the periphery of the wheel and forming a bed for the chain torest upon, which automatically tends to form a larger diameter than theactual pitch of the chain requires, thus allowing for a considerablestretch of the chain. The ends of the projections at the base of theteeth are recessed, so as to fit onto smaller projections formed at thebase on the opposite side of the tooth, thus interlocking each other, sothat the pressure and pull of the chain on the teeth in work cause thetooth about to enter the link of the chain to tilt backward and thetooth about to leave to tilt forward, allowing the chain to engage anddisengage with the least possible friction. The entering tooth isbrought into contact with the link directly the pressure of the go chainbears upon the extended portion at the base of the tooth, and theleaving tooth loses contact with the link as the pressure of the chainceases upon this extended portion.

.In order that our invention may be more clearly understood and easilycarried into practical effect, we append hereunto a sheet of drawings,upon which we have illustrated sufficient examples to show the nature ofour improved sprocket-wheels.

Figure 1 is a front elevation of a sprocket wheel made according to ourinvention. Fig. 2 is a similar view to Fig. 1, with the ring A removed.Fig. 3 is a plan view of Fig. 1. Fig. 4 is an enlarged view of one ofthe sprocketwheel teeth. Fig. 5 represents a portion of a sprocket-wheeladapted for a single-roller driving-chain. Figs. 6, 7, and 9 rep resentmodifications of our sprocket-wheels. Fig. 8 represents a cross-sectionof Fig. 1 on the line as '03.

Incarrying our invention into practice we form our sprocket-wheel of twomain partsthe wheel proper, A, and a ring A, which has its peripheryequal to that of the wheel A and V 'tirely open above and beneath. Inthis space,

on the same pivots which serve to rivet the rings A and 'A together, wepivot the teeth T, which teeth are free to rock or move and adjustthemselves to the variations in the pitch of the chain. These teeth,which we call lever-teeth, are formed wit-h the tailpiece or extendedportion 25- at their base, which forms that portion of the periphery ofthe wheel upon which the driving-links of the driving-chain rest, and atthe ends of this extended portion we form the slot '6 On the oppositeside of the base of these teeth we form the projections 25 whichprojections take into the slots '6 in the end of the tailpiece of thenext tooth. By these means it will be seen that all the teeth interlockeach other, so that the pressure or pu'll of the drivingchain on thoseteeth in engagement with the chain causes the tooth about to enter thelink,

of the chain to tilt backward and the tooth about to leave the link totilt forward with the least possible friction. The entering 2 w 62amtooth is brought into contact with the link directly the pressure of thechain bears upon the tailpiece t, and the leaving tooth loses contactwith the link as the pressure of the chain ceases upon the tailpiece.

The tailpiece of each tooth is very much longer than the distance fromthe pivot to the end of the forward projection.

As the teeth are all of the same size and form, it follows that there isa great difference inleverage in favor of the long tail as compared withthe part of the next tooth which engages it. Jonseqnently even a muchstronger pull on any one tooth will not suffice to depress the long tailt of the next tooth, l

but each succeeding tooth will be certainly and rapidly tilted by theforward pull of the chain, which necessarily lifts the tail thereof,tilting upward the next projection i strongly and certainly. Each recessis made broad enough to allow sufficient play of the projec tion 15which engages with it.

At Fig. 5 we have shown our sprocket-wheel I with the tailpiece of theteeth shortened, so as to bring the teeth closer together to form asprocketwheel suitable for single-roller I It will be quite evident thatinstead of forming the slot t in the end of the 1 tailpiece theprojection i may be formed at 1 this end and the slot 23 at the oppositeside 3 driving-chains.

near the base of the tooth.

At Figs. 6 and 7 we have shown two modi- 'fications of our lever-toothsprocket-wheels. In the method as shown at Fig. 6 we form i thetailpieces t and t at either side of each tooth, one of the tailpiecesbeing slotted at the end and the other being formed with a I projectionwhich takes into the slot in the tailpiece, of the next tooth. By thisarrange--' ment the tooth will tilt in either direction.

In the modification as shown at Fig. 7 inend of the tailpiece takes theexpanding action, being exactly similar, as previously described; or aprojection may be formed, as

shown in'Fig. 9, on the end of the tailpiece of each tooth and a slottedpiece fixed to the inner face of one or both of the rings A or A. Thesemodifications may be applied to the sprocket-wheel, as shown at Fig. 6.

We claim- 1. A sprocket-wheel provided at its periph- 5 5 ery with anannular series of pivoted teeth, each of which is provided with a longrearward tailpiece t having a terminal recess 25 and with a forwardprojection t the pivotal point of each tooth being under that part of itwhich is adapted to engage the chain, the recess 25 of each toothreceiving the projection t of the next one, and the recess 6 of eachtooth being much farther from the piv otal point thereof than is theprojection 25 of the same tooth, substantially as set forth.

2. A sprocket-wheel provided at its periphcry with an annular series ofpivoted teeth, each of which is provided with a long rearward tailpiecet having a terminal recess {2 and with a forward projection i arrangedto interlock with the recessed end of the next tooth, the recess t ofeach tooth being much farther from the pivotal point than is the projection t and also much broader than the pro- -7 5 jection interlockingwith the said recess, substantially as andfor the purpose set forth.

3. A sprocket-wheel provided at its periphery with a series of pivotedteeth, each tooth having a long rearward tailpiece and a shorter 8oforward part, each proximate tailpieceand forward part being adapted toengage each other. and thereby connect all the teeth in annular series,and the distance of the engaging part of each tailpiece from the pivotof the tooth being much greater than the distance of the end of theforward part of said tooth from the pivot thereof, substantially as setforth.

In testimony whereof we affix our signa 9o tures in presence of twoWitnesses.

THOMAS REGINALD VOCE. BRUCE DRYSDA'LE. lVitnesses:

GEORGE LESTER, E. S. FRIEND.

